1. Field of the Invention
This invention relates to a semiconductor device which has a semiconductor laser element, and functions to project a laser beam from the semiconductor laser element, while protecting the laser element.
2. Description of Prior Arts
It has heretofore been a practice to provide a casing (such as one designated by a reference numeral 1 in FIG. 1 of the accompanying drawings) about a semiconductor laser device for preventing environmental pollution, and to project a light beam as the laser output through an optical window 2 provided in the casing 1.
In view, however, of the fact that the semiconductor laser element 3 used in this device emits light beam from both ends thereof, there inevitably arises a problem that, rather than only one of the light beams, i.e., a front beam 4 alone, being projected out of the optical window as mentioned above, the other light beam, i.e., the rear beam 5, is also reflected within the casing 1 to mix with the front beam 4.
Thus, when the rear beam mixes with the front beam, a problem arises that no accurate measurement of the light beam from the semiconductor laser device can be made, because the light intensity differs from point to point on the optical window. Also, it is of great concern that ghost and other undesirable phenomena may occur depending on a positional relationship of the device at the time of its use. Such situations constitute inconveniences and disadvantages when the semiconductor laser device per se is evaluated, or when it is used as a recording device.